How different are exhausts on the inside?

[DaveGPz]

I'm sure this is a question that's been asked before, but I've been wondering (with an ulterior motive) just how different exhausts are between bikes of the same capacity. For example, is the exhaust from a CBR1000 going to be significantly different internally to one from a ZX10 or R1? For some reason, all available exhausts for my bike look like they've been designed by someone who thinks huge and round is good, and ideally the exhaust should stop the pegs scraping (actually, that was the GPz). So, would a cute little stubby GSX-R 1000 exhaust do evil things to a Sprint ST 955? You could beat whales to death with the standard one.

[Blurr]

you may find a performace drop to the reduced back pressure. You will also need to create o buy a mid pipe to make it fit all the corrrect mounting points. Other than that the baffles dont change between makes.

[DaveGPz]

Food for thought, food for thought. Cheers. I do miss the rumble of the Yoshi on the GPz1100, and I'm sure the Sprint could sound a whole lot nicer, but at the cost of performance? Hmmmm...

[knightrook]

besides sticking an exhaust from another bike on, is there much performance difference between exhausts for the same bike? Would a yoshi exhaust for a zx9 be better than a remus? Or is it only a difference in sound... Just out of curiosity...

[Smitty]

I'm sure this is a question that's been asked before, but I've been wondering (with an ulterior motive) just how different exhausts are between bikes of the same capacity. For example, is the exhaust from a CBR1000 going to be significantly different internally to one from a ZX10 or R1? For some reason, all available exhausts for my bike look like they've been designed by someone who thinks huge and round is good, and ideally the exhaust should stop the pegs scraping (actually, that was the GPz). So, would a cute little stubby GSX-R 1000 exhaust do evil things to a Sprint ST 955? You could beat whales to death with the standard one.

Dave
it comes down to engine design...stuff like valve angles cam overlap etc
plus the actual exhaust port size and direction (bends etc) which dictate what
SHOULD be used as an exhaust (on a road bike...race bikes can be different)

the exhaust piping itself will be pretty much the same (round tubing) but may be bent or directed differently
to fit in or around the chassis and then off to some sort of collector/sound box/muffler/cat converter
In most cases on a road bike again all this is a compromise and the factor of cost has to be introduced
as well as compliance with ADRs and EPA requirements......


and no a Gixxer thou zorst wont do wonders for a ST995.... fiting it for a start would be a PITA

[DaveGPz]

Fairs nuff; might be back to plan A and a Staintune oval pipe.

[IsleofNinja]

Fairs nuff; might be back to plan A and a Staintune oval pipe.

>What/how does the stock can fit to the mid pipe Dave?ie slip on/bolt on?
>Assuming it's a slip on, most are a 2 1/4" pipe dia over 600cc.

Power curve and zorst note depend on :
-core pipe dia
-core pipe perforations
-core length
-Outer can dia
-Packing material/density.
-exit pipe / no exit pipe (end cap only)
and so forth.......

Maybe not quite so much hocus pocus as you might think consider for example a Yoshi tri oval to suit a 99ZX6r for example is the EXACT muffler configuration as sold to suit say a 04 ZX12r - only difference is the mounting nipple/flange.
ie generally street bike muffler manufacturers keep the design from bike to bike as generic as possible to keep costs down.

Sorry Smitty but I think you were actually refering to custom race bike zorsts mate - often exotic one off items built to obtain the desired engine characteristics.

[photomike666]

I've opened two road bike silencers over the years. The first was a stock Yamaha can from an FZx750, the second a Staintune for my CBR600.

The Yamaha can consisted of 3 perforated pipes linking between an entry chamber, a mid chamber and the exit. Each pipe was surrounded by baffling material. This gave the silencer, effectivly three times it's lenght in silencing ability.

The Staintune was simply a straight through perforated pipe surrounded by baffling. It also came with a plug that effectivly reduced the size of the exit, and pushed some of the exhaust gas back through the baffling.

I am sure that there are a variety of differing designs, with various size perforated pipes, chambers and baffling thickness. Each design will effect gas pressure very differently, and thus effect the engine performance. I would also expect each silencer is tuned to that particular engine dynamic.

[DaveGPz]

The Pipeline that came on my FJ1100 was spectacularly (painfully) loud, and was of the straight-through perforated pipe type. Not quite on a par with the "If your ears ain't bleeding, the bike's not running" Harley philosophy, but it did make the windows rattle. I'm more after the rumble/roar of the 4-1 Yoshi I put on the GPz1100 (which was sourced from a ZZR1100, which has a different top-end, and which started me thinking about this whole pipe difference thing in the first place)

It's hard to imagine that a manufacturer like Yoshimura would have different can internals for a ZX9, ZX10, CBR1000, GSX-R1000 etc. It'd be interesting to look at part numbers for slip-ons...

...even more interesting to see if a muffler for a VTR1000 was different internally to one from a CBR1000; wondering if the engine configuration makes a huge difference; Inline 4, triple, V-twin? Might look up some wrecked cans from my mate at the wreckers and have a look inside.

[photomike666]

4-1, 4-2, 4-1-2 etc all have different back pressures and effect power production - often where in the rev range the power is produced. This will be done in conjunction with head design and valve timing.

Also, each can has to be designed for the particular bike, as the feed pipes and mounting points are different. It may well be that most race silencers are of similar design, aimed for top end power, where tourer pipes would all be similar to produce better mid range power. Headers are designed to give the same gas flow lenght from the cylinder to the tailpipe for each cylinder. Real trick headers have bends to enhance flow rates and back pressures.

[DaveGPz]

So the 'custom exhausts' you read about that some legend has knocked up in his shed ala Bert Munro could be the worst thing ever, designed with form over function and either strangling the engine or killing the bottom-end with low back pressure.

[photomike666]

That is entierly possible, unless of course they understand exhausts far better than you and I.

[DaveGPz]

OK. I'll put my pyjamas back on and crawl back under my rock; which reminds me - my son (on the blue FZR250) told me to remember that when we went on the pyjama ride we had leather underwear. Faintly disturbing, that boy...

Anyone had any experience with Two Brothers Racing exhausts?

[Gosling1]

...So the 'custom exhausts' you read about that some legend has knocked up in his shed ala Bert Munro could be the worst thing ever, designed with form over function and either strangling the engine or killing the bottom-end with low back pressure......

If the backyard legend has NFI about what he is doing - then yes, an exhaust knocked up in the shed is unlikely to flow better than one off the shelf...

I have made a few exhaust systems over the years, mainly 4-1 systems for old air-cooled kwakka's.......I get my car local exhaust bloke to buy in the 8 mandrel-bend pieces you need for a 4-1, and also the collector box to my specs - then just weld it all up, make up the mid-pipe to the muffler....and away we go.

Its not really a black art, there are certain physical limitations to *how* an exhaust works - eg - most 4-stroke engines with a red-line of 10,000rpm will have a 'tuned-length' of around 27" from exhaust port to end of header pipe (ie collector box inlet). It will vary a 'bit' around this figure, but not by much. As you increase the max RPM amount, then the tuned-length of the header pipe will vary....

If you haven't yet read 'Tuning for Speed' by Phil Irving - get a copy and digest it - it has a lot of great info in it.....

As far as exhausts on the inside ?? They are all much the same from the exhaust port to the muffler. A round pipe that just routes exhaust gas (and noise) back to the muffler. The design of the pipe is more about look than anything else really . The muffler does exactly that - it muffles the noise produced by the motor. Some of them (ie the 'absorption' muffler - straight-through design with packing) are the noisiest, but also flow the best. These need to have the jetting/FI tuned to suit the better flow. The other style with multiple chambers (generally OEM style) are made to keep the bike really quiet and under dB limits for ADR compliance. Every manufacturer has their own 'design' of muffler, but they all do much the same job.

I won't get into any discussions about 'back-pressure' and 4-stroke motors..... unless of course you want to discuss 2-stroke exhausts - this is where back-pressure discussions actually belong....

[DaveGPz]

I won't get into any discussions about 'back-pressure' and 4-stroke motors..... unless of course you want to discuss 2-stroke exhausts - this is where back-pressure discussions actually belong....

...or boy racers with turbo Lancers or WRXs and exhausts the size of wheelie-bins - enter the world of turbo-lag!